Abstraction is a necessary process in human thought.
Abstraction literally means “from-pulling.” The human mind pulls information from a source. Let us take an example:
I am in a room looking at a table, which has some cheese on it. My mind is directed towards the cheese on the table and is picking up the visual sense data. Of course, the mental representation in my head contains far more information than the simple fact that the cheese is on the table: for instance, I know that the table is round not rectangular. Yet, using some principle of selection, plus pre-existing concepts in my mind (cheese, on-ness, table), I can abstract that single piece of information, namely, the cheese is on the table. And using linguistic terms which correspond to the concepts in my mind, I can form the proposition: “The cheese is on the table.”
The proposition, “The cheese is on the table.” is an abstraction from a perception. It is, by necessity, quite different from its source, even if it is dependent on its source for its existence and truth value. Let us look at three points:
1. The abstraction is based on the exclusion of information (e.g. the table is round). The decision of what to include in the proposition depends on a principle external to both the observation and statement.
2. The abstraction relies on concepts (e.g. cheese,on-ness, table), which are external to the observation.
3. The statement, “The cheese is on the table.” can be understood but not accurately visualised by a listener or reader. He knows what the proposition means, but he cannot visualise a table without knowing its shape, colour, etc.
Secondary abstraction involves the extraction of information from one statement and the creation of another. A simple example would be: “The Gouda cheese is on the round table” and deriving “The cheese is on the table.”